The mass production of blocks is often carried out by filling a mold for a preset period of time with a green concrete mixture and compacting the mixture into a mold for a second pre-set period of time before releasing the mold and removing the molded blocks from the apparatus. Commonly, the compaction of a green concrete mixture is accompanied by vibration in order to ensure that the mixture is uniformly distributed in the mold cavity and to minimize the occurrence of void pockets. The process works well for most masonry applications, such as blocks, bricks, and slabs where mortar is used to compensate for minor irregularities in the dimensions of the finished product of up to .+-.3 mm.
In the case of mortarless blocks, where projections and corresponding recesses are provided in the blocks to interlock adjacent courses of blocks without any mortar, the dimensional tolerances are much smaller and should not exceed 1 mm in order for the blocks to stack properly without loss of structural integrity and strength.
It is therefore desirable to provide more controls into a block molding process to obtain the necessary dimensional tolerances while maintaining density without loss of productivity.